Luminescence properties of Tb3+:Y3Al5O12 nanocrystallites prepared by the sol–gel method

Tb 3+ :YAG nanocrystalline powders have been prepared by the sol-gel route. Structure and morphology of the obtained materials have been studied. The average grain sizes have been determined by X-ray powder diffraction measurements. Photo- and cathodoluminescence spectra of the Tb 3+ :Y 3 Al 5 O 12 powders have been measured. It has been found that the samples at low concentration demonstrate emission ascribable to the 5 D 3 →F J and 5 D 4 → 7 F J transitions. In particular, the concentration dependence of the luminescence spectra and lifetimes have been investigated as a function of the YAG grains sizes. It has been shown that the cross-relaxation responsible for the quenching of the 5 D 3…

Microwave-Driven Hydrothermal Synthesis of Oxide Nanopowders for Applications in Optoelectronics

Spectroscopic studies of 5,5′-dimethoxy-3,3,′-disulfobutyl-9-ethylthiacarbocyanine (DDTC) in solutions and immobilized in sol-gel matrices

Abstract Absorption spectra of 5,5′-dimethoxy-3,3,′-disulfobutyl-9-ethylthiacarbocyanine (DDTC) in aqueous solutions and immobilized in xerogels prepared by the sol-gel method were obtained. Influence of pH, detergent (Triton X-100), ethanol addition and sol-gel preparation method on the dye aggregation equilibria and its photostability were investigated. In liquid solutions lowering of pH, as well as addition of the detergent, shift the aggregation equilibrium towards the DDTC monomeric form. However, while more acidic conditions result in a decrease of the dye stability, addition of the detergent has a slightly stabilizing effect on the dye. However, addition of ethanol drastically reduce…

Spectroscopic and electrochromical properties of metallophthalocyanines in silicate bulks and thin films prepared by the sol–gel method

Abstract Magnesium phthalocyanine (MgPc) and praseodymium bisphthalocyanine (Pr(Pc) 2 ) have been entrapped in bulks and thin films of porous silicate xerogels prepared via the sol–gel method. The electronic absorption data obtained for the complexes immobilized in bulk sol–gel matrices indicate the formation of complex equilibria between their monomeric forms and respective agglomerates. Thin xerogel films doped with metallophthalocyanines and connecting two slides of transparent ITO electrodes display changes in the absorption spectra caused by varying of the applied voltage. These changes appear to be reversible in certain ranges of the applied voltages.

Physicochemical properties of Ru(bpy)32+ entrapped in silicate bulks and fiber thin films prepared by the sol–gel method

Silicate porous xerogels doped with ruthenium bipyridine (Ru(bpy)32+) complex have been obtained in the bulk form and in thin films on optical fibers. The hypsochromic shifts in the absorption and emission maxima are accompanied by fourfold increase in the lifetimes of the entrapped complex. The temperature-dependent lifetimes reveal that silicate xerogels induce two competing thermally activated processes in the excited state decay of the immobilized complex. The excited state lifetimes of the doped bulk xerogels and the fibers coated with thin films containing Ru(bpy)32+ are virtually identical to those obtained for the fibers coated with additional gas-impermeable layers.

The time-resolved luminescence characteristics of Ce and Ce/Pr doped YAG ceramics obtained by high pressure technique

Abstract Transparent Ce and Ce/Pr doped YAG ceramics were prepared under high pressures (up to 8 GPa) and relative low temperature (450 °C). Grain size of the ceramics is less than 50 nm. However unknown defects or disorders strains on grain boundaries caused the additional absorption in these ceramics. The luminescence intensity, spectra and the decay time dependence on pressure applied during ceramic preparation were studied. Concentration of some intrinsic point defect was reduced under the high pressure applied for sintering process. It is shown that formation time of the excited state of Ce luminescence depends on the pressure applied during ceramic sintering.

Optical behavior of Eu3+-doped BaTiO3 nano-crystallites prepared by sol–gel method

Abstract Eu 3+ -doped BaTiO 3 nano-crystallites with grain sizes 32–38 nm have been obtained by a sol–gel method. It has been found that the luminescence characteristics are strongly dependent on the sintering temperature. Powders sintered at temperatures below 1000 °C demonstrate a luminescence behavior at room temperature associated with a lack of the inversion symmetry of Eu 3+ sites. Above 1000 °C nano-crystallites undergo a phase transition characterized by an inversion symmetry of Eu 3+ sites. The size effect of Eu 3+ :BaTiO 3 nano-crystallites on luminescence characteristics is observed.